The impact of the partitioning of oxygenation markers (perfluorocarbons) between blood and tissue in fluor-19 MRI oximetry is evaluated through computer simulations. The simulation studies the correspondence between actual and fluor-19 MRI measured oxygen tension. Simulation results indicate that the blood-tissue partitioning of perfluorocarbons has a serious impact on the deviations between actual and fluor-19 measured oxygen tensions. In addition, perfluorocarbon presence in blood influences the actual oxygen tension as compared to a situation without perfluorocarbons. Fluor-19 MRI oximetry can be applied to map oxygen concentrations in hypoxic tumor tissues, which are well known to reduce cancer treatment efficacy.